Generate a username during checkout for user [Paid Memberships Pro]

generate-username-from-first-and-last-name-pmpro.php

<?php
/**
 * Generate a username at PMPro checkout from first and last name for users.
 * Hide your 'username' field using custom CSS.
 * Add this code to your site by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

 function my_pmpro_generate_username_at_checkout() {

	//check for level as well to make sure we're on checkout page
	if (empty($_REQUEST['level'])) {
		return;
	}

	if ( !empty($_REQUEST['first_name']) && !empty($_REQUEST['last_name']) ) {
		$_REQUEST['username'] = my_pmpro_generate_username_from_email( $_REQUEST['first_name'],  $_REQUEST['last_name'] );
	}

	if (!empty($_POST['first_name']) && !empty($_POST['last_name']) ) {
		$_POST['username'] = my_pmpro_generate_username_from_email($_POST['first_name'], $_POST['last_name']);
	}

	if (!empty($_GET['first_name']) && !empty($_GET['last_name']) ) {
		$_GET['username'] = my_pmpro_generate_username_from_email($_GET['first_name'], $_GET['last_name']);
	}

}
add_action('init', 'my_pmpro_generate_username_at_checkout');

/**
 * Hide the username field on checkout.
 */
function my_pmpro_unset_required_username_checkout( $pmpro_required_user_fields ) {
	unset( $pmpro_required_user_fields['username'] );
	return $pmpro_required_user_fields;
}
add_filter('pmpro_required_user_fields', 'my_pmpro_unset_required_username_checkout', 10, 2);


/**
 * Generate a username from a user's  first and last name.
 * Helper function.
 */
function my_pmpro_generate_username_from_email($first_name, $last_name) {
	$proposed_name = sanitize_text_field( strtolower( $first_name ) . '.' .  strtolower( $last_name ) );
	$user_name_already_exists = get_user_by( 'login', $proposed_name  );
	if(! $user_name_already_exists ) {
			return $proposed_name;
	} else {
		return $proposed_name . pmpro_getDiscountCode();
	}
}